Study On The Seepage Law Of Gas Containing Coal Under Different Temperature And Creep Condition

Injecting heat to increase the production of coalbed gas is a promising way.When injecting heat,coal will inevitably produce heat creep with the effect of long-term heat and this heat creep will inevitably have important effect on permeability of coal containing gas.In order to explore the influence of temperature on seepage of coal containing gas,this paper has carried out a series of studies.By using three axis coal rock rheological test system,the whole stress-strain experiment of coal containing gas under different temperature has been carried out,and the coal permeability has been measured in the whole process.The experimental results show that with the stress increasing,in the earlier stage the axial strain is dominant,the coal body is gradually compressed,and the permeability decreases.While in the later stage,the radial strain is dominant,the coal body swelling to radial,the volume gradually increase,and the permeability increases.At the same time,the loading creep stress of creep-seepage experiment is determined by the whole stress-strain experiment.The creep-seepage experiment of coal containing gas and the He contrast experiment have been carried out in different temperature and gas pressure.The experimental results show that:Under constant temperature,the gas pressure increases,the creep deformation of coal containing gas increases.The gas pressure is the main reason of the reduction of strength of coal body,and gas adsorption would affect the creep but it's not the dominant factors.Under constant gas pressure,in the different creep lines of coal containing gas in different temperature,the differences of axial strain are not obvious and even some overlaps appear.However,the differences of radial strain are more obvious.The radial strain will increases with the temperature increasing.The effect of temperature on gas adsorption is that when in high gas pressure,the temperature influence is weak and the gas pressure dominate the adsorption.When in low gas pressure,the temperature influence is obvious,and the temperature dominates the adsorption.In comparation,for gas,the influence of high temperature on axial strain is obvious in lower gas pressure.However,for He,the influence is obvious in higher gas pressure.After creep of coal containing gas,the permeability decreases.The higher the temperature is,the smaller the permeability is after creep.The higher the gas pressure is,the smaller the permeability is after creep.The He contrast experiment also come to this conclusion,which means that the gas adsorption does not play a leading role and it does not change the trend of permeability.Learning the studies of the former researchers,the creep equation of coal containing gas which reflects the volume strain was provided.According to the Kozeny-Carman equation and the creep equation,the permeability model has been derived and it fit better that can predict the development regularity of permeability.Drawn from the relationship between permeability and volume strain under different temperature,the permeability of coal decreases when the volume strain increases.At the same time,under constant gas pressure,the higher the temperature is,the smaller the permeability of coal is..